Cherie Blair found herself being steered through the audience towards the back of the room. She had just finished speaking about the 'empowerment of women' and was smiling, in her bashful way, at the enthusiastic applause.

Instead she delivered Mrs Blair straight to an exotic blonde woman standing, incongruously among 70 or so lawyers and human-rights activists, with her pop-star husband. Mrs Hauserman, whose charity was hosting the function, announced that the woman, Dwina, was someone Cherie simply had to meet.

As she predicted, they got on famously because - although the reasons may not seem immediately clear - they had 'a lot in common'.

And so began, a year ago almost to the day, Mrs Blair's extraordinary friendship with Dwina Murphy-Gibb: erotic artist, one-time fetish- magazine model, part-time Druid priestess and bisexual.

The Mail on Sunday can reveal that Mrs Blair's association with Dwina, the wife of Bee Gees singer Robin Gibb, extends way beyond their much publicised festive holiday in Miami.

They have grown close over the past year and are understood to have met several times at Downing Street.

In fact, it would appear to many in Mrs Blair's circle that American businesswoman Martha Greene - her friend, agent, travelling companion and 'fixer' - has been usurped by Irish-born Dwina.

Sources close to Mrs Greene play down these suggestions but there is no denying that, where the former advertising executive was once a ubiquitous figure at No10, she is now seen much less frequently at Mrs Blair's side.

To add further weight to Dwina's 'lady-in-waiting' status, callers enquiring about Mrs Blair's public speaking engagements, who were once referred to Mrs Greene, are now told to write instead to 'the Prime Minister's office'.

Even by the standards of some of Mrs Blair's previous friends - former glamour model Carole Caplin, for instance - Dwina's past is colourful almost beyond belief. But there is something else - potentially dangerous - that yet again places a question mark against Mrs Blair's judgment and the almost kamikaze, ill-advised way she embarks on certain friendships.

It is Dwina's close involvement with Brahma Kumaris, a women-led spiritual organisation that, while striving for world peace, has allegedly used 'pernicious' methods to control its followers.

The group is led by 90-year-old Indian spiritualist Dadi Janki, a woman Dwina regards as her guru and whom she consults, according to a source close to her, 'about everything'. Both Dwina and Robin make regular donations to Brahma Kumaris, which translated means Daughters of Brahma, the Hindu god of creation.

But besides its concern for world peace, the organisation is also notable for its sex ban. "Former members and the families of members have told me that Brahma has driven a wedge between husband and wife,' said Graham Baldwin, a cult expert who has counselled former Brahma members.

"There have also been complaints that it encourages single women and widows to donate property and savings to Brahma and move into a group house."

Brahma Kumaris demands celibacy because 'sexual intercourse, while capable of being an expression of love at the human level...pulls our consciousness firmly into the material domain'.

Ian Howarth, of the Cult Information Centre, said: "I have the same concerns about this group that I have about the Moonies. People have come to us complaining that some loved ones who have got involved with it have undergone personality changes and have become alienated from their families."

The organisation confirmed to The Mail on Sunday that Dadi Janki had met Mrs Blair at a function organised by the charity Rights and Humanity UK. Both are patrons of the charity and Dwina is also closely involved.

It was Rights and Humanity, led by Julia Hauserman, that hosted the meeting Mrs Blair addressed last January. It describes itself as a multi-faith international movement that aims to protect human rights and dignity. Mrs Blair is its Women's Human Rights and Empowerment Network Patron.

Lynne Franks, the former PR queen on whom the Bollinger-swigging Absolutely Fabulous character Edina is based, also has close ties to both Brahma Kumaris and Rights and Humanity.

Now a self-styled lifestyle guru and 'visionary', she is the founder of a network called SEED, which runs 'empowerment programmes' for women. On at least one occasion SEED has jointly staged an event with Brahma Kumaris, which Dwina attended.

Asked exactly what Mrs Blair and Dwina have 'in common', Mrs Hauserman explained: "They are both very committed to the rights of women and empowering women. They have since become good friends and both have spoken at a number of our events.

"Dwina has even read some of her poetry, which has been much appreciated by our audiences. Mrs Blair, as our chief patron, has also hosted a number of meetings in Downing Street."

The most recent, classed as a private discussion, took place in December and 53-year-old Dwina was one of the guests.

"They really do have a lot in common, and as friends they speak to each other often,' said Mrs Hauserman, who founded Rights and Humanity 20 years ago.

She knew in advance of the Blairs' controversial stay at the Gibbs' £5.2million beach house. And she confided that the arrangements had been made by Mrs Blair and Dwina, making it clear it was not the Prime Minister's friendship with Robin Gibb that brought the Blairs to Miami.

The Bee Gee is also a follower of Dadi Janki and credits her with helping him overcome the death of his twin brother Maurice in 2003. Both he and Dwina wear red lapel pins with a tiny diamond to represent the point of light Brahma Kumaris members use as a focus for meditation. Once asked what she thought of the "BKs', Dwina replied: "They are living, walking angels on this earth. They can help us become angels too."

A spokeswoman for Dadi Janki confirmed that Dwina had been a regular visitor to the Brahma Kumaris global retreat in Oxfordshire, but was unaware of her ever being joined by Mrs Blair. Speaking from India, the spokeswoman added: "Dadi Janki briefly met Mrs Blair at a function organised by Rights and Humanity, but as far as we are aware Mrs Blair has not expressed an interest in meditation.

"Mrs Gibb, however, does. She has met Dadi Janki on a number of occasions."

Is Mrs Blair, perhaps under the influence of her exotic friend, in danger of being drawn into the world of Brahma Kumaris?

It does not require a great leap of imagination to see this as a possibility: her fascination with alternative therapies such as crystal healing and 'thought field therapy' is well documented, as is her interest in India, particularly its female population.

No doubt Dwina would be delighted to recruit her. And if Dwina has been successful in displacing Martha Greene, it would represent another remarkable milestone in her life.

She has come a long way from the modest bungalow in a remote Northern Irish village where she was born and raised. Her elderly widowed mother Sarah still lives in the house in Kilskeery, County Tyrone.

Undoubtedly, the more outrageous aspects of Dwina's lifestyle would raise eyebrows among the strict Catholic community.

"I'm not going to talk about her - I'm not that kind of person at all, at all,' said her mother with a chuckle. Asked about her daughter's association with Cherie Blair, she would say only: "They're just friendly, that's all. They do charity work together."

Dwina left Kilskeery in the early Seventies, moving to London where she was free to indulge her outlandish tastes. By the mid-Seventies, she was an established fixture on the capital's 'alternative' scene.

Gillian Lee, a friend from this period, told The Mail on Sunday: "I first met Dwina at the flat of an accountant called David in Belsize Park. David was teaching people Kabbalah, and Dwina was interested in learning as much as she could. She used to wear her hair dyed all the colours of the rainbow in concentric rings.

"I was given the impression that she was having a sexual relationship with David. At the time I was also studying Kabbalah. Together with David and a number of other people we frequently met for Kabbalistic study and the practice of magical ceremonies.

"Later she moved to a house in Plumstead which she shared with a man called Andrew, who was also into Kabbalah. He grew Psilocybe magic mushrooms and believed he was the anti-Christ. He also built a dome inside his house in which he and Dwina inhaled oxygen.

"At the time her cousin was working as a bodyguard for Robin Gibb, and he arranged a meeting for her."

According to Dwina, who was then trying to make it as an artist, she impressed Robin with her drawings. The couple married in 1985 and have an open relationship.

"I knew Dwina was gay when we married but that doesn't matter because I was in love with her,' Robin has declared. "And, anyway, she is bisexual with me. She's the best wife any husband could want."

Asked about the allegation that Brahma Kumaris has wrecked marriages because of its sex ban, a spokeswoman said: "This is very much a minority thing. In any organisation there are people who gain a huge amount and that is what you need to focus on."

She declined to comment on allegations that it encourages followers to donate property and savings.